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Molecular dynamics simulation study of a polymer droplet transport over an array of spherical nanoparticles

The dynamic behavior of a partially wetting polymer droplet driven over a nanostructured interface is studied using molecular dynamics simulations. We consider the bead-spring model to represent a polymeric liquid that partially wets a rough surface composed of a periodic array of spherical particles. It is shown that at sufficiently small values of the external force, the droplet remains pinned at the particles' surface, while above the threshold, its motion consists of alternating periods of pinning and rapid displacements between neighboring particles. The latter process involves large periodic variation of the advancing and receding contact angles due to attachment and detachment of the contact line. Finally, upon increasing external force, the droplet center of mass is displaced steadily but the oscillation amplitude of the receding contact angle as well as the maximum contact angle hysteresis remain relatively unaffected.